The present invention relates to a tubular member forming the cylinder of liner type shock absorbers and a knuckle bracket constructed from sheet metal and relates to a strut for McPherson type automobile suspensions, wherein the said knuckle bracket parts for fitting the bearing bush, i.e., the bearing spindle of the wheel brake and the said tubular member are fitted at the lower end in the through hole of the said knuckle bracket and fixed forced-push fitting, welding or other means.
Constructions of such a type are well-known, for instance, from U.S. Pat. No. 3,941,401. The knuckle bracket of the strut described in this specification is formed from sheet metal and therefore it is better in that it offers low in manufacturing costs and light weight compared with the common knuckle brackets which are formed from forged steel or cast iron. In addition, it is general knowledge that a cylindrical axle bracket is already being used in practice which has a bracket part for fitting the knuckle spindle at one side of a strut formed by the first bracket with a U-shaped cross-section covering three fourths of the outer circumference of a tubular member in a strut and the second brackt with a -shaped cross-section fitted in the opening part of the first bracket.
However, where these well-known struts for McPherson type suspensions are used in practice, the maximum bending stress is applied to that part of the tubular member which is fitted in the upper end of the knuckle bracket. Since the bending force occurring between the tubular member and the knuckle bracket causes the corresponding part of the tubular member to deform elastically with repeated vibration occuring, cracks or fractures may develop in the tubular member due to bending fatigue and there is a danger of automobile suspensions breaking, thus causing serious danger.
These defects may be lessened by increasing the thickness of the particular part of the conventional above-mentioned tubular members or by welding a reinforcing sleeve fitted to the particular part of the tubular members as disclosed in the Specification of U.S. Pat. No. 3,430,977; however, such means will nullify the low cost and weight advantages to be obtained with the use of a knuckle bracket formed from sheet metal.